Apparatus for carbon fiber processing and pitch densification

ABSTRACT

A pitch densification apparatus may be used to form a carbon-carbon composite material. The apparatus may be used to compress a carbon fiber material, and, thereafter, pitch densify the carbon fiber material. The compression and pitch densification of the carbon fiber material may be carried out within the same mold cavity of the pitch densification apparatus. In one example, an apparatus may comprise a mold defining a mold cavity that is configured to receive a material to be densified. The mold cavity is configured to be adjusted from a first volume to a second volume less than the first volume to compress the material in the mold cavity. The example apparatus may further comprise a gas source configured to apply a gas pressure in the mold cavity to force pitch into the material in the mold cavity to densify the material, and a vacuum source configured to create a vacuum pressure in the mold cavity at least prior to the application of the gas pressure.

TECHNICAL FIELD

This disclosure relates to pitch densification and, more particularly,to pitch densification for carbon-carbon composites.

BACKGROUND

Carbon fiber-reinforced carbon materials, also referred to ascarbon-carbon (C—C) materials, are composite materials that generallyinclude carbon fibers reinforced in a matrix of carbon material. The C—Ccomposite materials are found in many rigorous, high temperatureapplications. For example, the aerospace industry is known to employ C—Ccomposite materials for manufacturing different aircraft structuralcomponents. Example applications include rocket nozzles, nose cones, andfriction materials for commercial and military aircraft such as, e.g.,brake friction materials.

SUMMARY

In general, the disclosure relates to apparatuses and techniques forprocessing fiber materials and densifying the processed fiber materialswith pitch. In some examples, a single apparatus may be configured toreceive a carbon fiber material, compress the carbon fiber material, anddensify the compressed carbon fiber material with pitch. The apparatusmay perform the different processing steps without removing the materialfrom the apparatus.

In one example according to the disclosure, an apparatus includes a molddefining a mold cavity configured to receive a material to be densified,where the mold cavity is configured to be adjusted from a first volumeto a second volume less than the first volume to compress the materialin the mold cavity. The apparatus also includes a gas source configuredto apply a gas pressure in the mold cavity to force pitch into thematerial in the mold cavity to densify the material, and a vacuum sourceconfigured to create a vacuum pressure in the mold cavity at least priorto the application of the gas pressure.

In another example according to the disclosure, a method is disclosedthat includes inserting a material to be densified into a mold cavity ofan apparatus, wherein the apparatus is configured to densify thematerial within the mold cavity using a vacuum pressure infiltrationcycle; compressing the material in the mold cavity by adjusting the moldcavity from a first volume to a second volume less than the firstvolume; and pitch densifying the compressed material in the mold cavityusing the vacuum pressure infiltration cycle.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating of an example aircraft brakeassembly.

FIG. 2 is a conceptual block diagram illustrating an example apparatusconfigured to process and pitch densify a carbon fiber material.

FIGS. 3A and 3B are conceptual diagrams illustrating of example segmentsof carbon fiber material that may be used in the example apparatus ofFIG. 2.

FIGS. 4A and 4B are conceptual diagrams illustrating example surfacesthat may be combined to form an example mold cavity for an example moldthat may be used with the example apparatus of FIG. 2.

FIG. 5 is a conceptual diagram illustrating a cross-sectional view ofthe example mold cavity.

FIGS. 6A and 6B are schematic diagrams illustrating an example apparatusconfigured to process and pitch densify a carbon fiber material.

FIG. 7 is a flow diagram of an example method for processing and pitchdensifying a material within a single apparatus.

DETAILED DESCRIPTION

In general, the disclosure relates to apparatuses and techniques forprocessing fibrous material and densifying the processed fibrousmaterials with pitch. In some examples, a single apparatus may beconfigured to receive a carbon-based fiber material (also referred toherein as a “carbon fiber material”), compress the carbon fibermaterial, and densify the compressed carbon fiber material with pitch.The apparatus may be configured such that the carbon fiber material maybe compressed and densified with pitch within the same mold cavity ofthe apparatus.

To process a carbon fiber material using such an example apparatus, thematerial may be inserted within a mold cavity. The volume of the moldcavity may then be reduced to compress the carbon fiber material locatedwithin the mold cavity. The compression of the carbon material byreducing the mold cavity volume serves to increase the fiber volume ofthe carbon material in the mold cavity. Put another way, the fiberdensity within the mold cavity is increased since the overall volume ofthe mold cavity is reduced while the amount of fiber material in themold cavity is substantially constant. In practice, the volume of themold cavity may be reduced to provide for a desired fiber volume of thecarbon fiber material in the mold.

Following the compression of the carbon fiber material, the apparatusmay be configured to thereafter impregnate the carbon fiber materialwith pitch within the mold cavity of the apparatus using gas pressure,vacuum pressure, or a combination of gas pressure and vacuum pressure.For instance, after the material has been compressed in the mold cavity,the apparatus may be configured to impregnate the carbon fiber materialin the mold cavity using a combination of gas pressure and vacuumpressure during one or more vacuum pressure infiltration (VPI) cycles.In some examples, depending on the particular material used, the carbonfiber material may optionally be needled within the mold cavity toentangle different carbon fibers of the carbon fiber material prior tobeing impregnated with pitch (e.g., prior to being compressed within themold cavity).

For instances in which a carbon fiber material is compressed by reducingthe volume of the mold cavity and then densified in the same moldcavity, the carbon fiber material does not need to be inserted into apreform fabrication apparatuses to be fabricated into a preform (whichmay include compression and/or carbonization of the carbon material),removed from the first preform apparatus, and then inserted anddensified in a separate pitch densification apparatus. Instead,compression and densification processes may be performed on a carbonfiber material within the same apparatus. Because such an exampleapparatus does not require a carbon fiber material that is firstfabricated into a preform in a first apparatus to be removed andinserted into a second apparatus for densification, the apparatus mayeliminate one or more processing steps during the fabrication of a C—Ccomposite component.

In some examples, an apparatus in accordance with the disclosure mayprocess carbon fiber materials that may not otherwise be readilyfabricated into a preform. For example, an example apparatus inaccordance with the disclosure may process carbonized fibers (carbonand/or carbonatious fibers that have been carbonized) or pitch fibers(fibers constructed of pitch material), which are generally too brittleto manufacture into a preform. In some instances, because an exampleapparatus may process carbonized fibers, pitch fibers, or the like, theneed for a separate apparatus to perform processing steps such aspreform fabrication or carbonization may be eliminated.

In some instances, to fabricate a C—C composite material component, acarbon-based fiber material may undergo multiple processing steps indifferent apparatuses to arrange, strengthen, and densify the carbonfiber material into a formed component. For example, a carbon fibermaterial may be processed into a carbon preform using one or moreapparatuses. The preform processing steps may add mechanical strength tothe carbon fiber material to prepare the carbon fiber material toreceive pressurized pitch during pitch densification.

In different examples, a carbon fiber material may be processed into apreform by arranging the carbon fiber material into the shape of afinished component, adding a binder, e.g., a phenolic resin, to thematerial, needling the material, and/or carbonizing the material. Suchprocessing steps may each be performed on separate respectiveapparatuses. For example, in cases in which oxidized PAN fiber is used,after being arranged into the shape of a finished component and needledon one or more apparatuses, the carbon material may be transferred to aseparate carbonization apparatus. The carbonization apparatus maycarbonize the polyacrylonitrile (PAN) fibers by heating the material inan inert atmosphere to remove non-carbon elements (e.g., H, N, O, S, orthe like) and other impurities from the material. In this manner, thecarbon fiber material may be fabricated into a preform.

After transforming the carbon fiber material into a preform, in someexamples, the preform may be transferred to a separate apparatus forpitch densification. For example the preform may be transferred to anapparatus that is capable of impregnating the preform with pitch viaresin transfer molding (RTM) or vacuum pressure infiltration (VPI). Inthis manner, the preform may be further processed into a C—C compositematerial. Overall, such processing requires multiple differentapparatuses to fabricate a C—C composite material from

In accordance with some examples described in this disclosure, anapparatus may be configured to both process a carbon fiber material toreceive pitch and to impregnate the processed carbon fiber material withpitch. In some examples, the carbon fiber material may be inserted intoa mold cavity of the apparatus and compressed within the mold cavity. Insome examples, the carbon fiber material inserted and compressed withinthe mold cavity may include fiber material that has been carbonizedprior to being inserted in the mold cavity. Examples of such materialmay include carbonized PAN fibers, carbonized pitch fibers, carbonizedrayon fibers, and the like.

After compressing the carbon fiber material in the mold cavity, theapparatus may be configured to thereafter impregnate the carbon fibermaterial with pitch within the same mold cavity using gas pressure,vacuum pressure, or a combination of gas pressure and vacuum pressure.For instance, the apparatus may be configured to impregnate the carbonfiber material with a combination of gas pressure and vacuum pressureusing one or more vacuum pressure infiltration (VPI) cycles. In thismanner, the apparatus may process a carbon fiber material by compressingthe carbon material and also impregnating the material with pitch withinthe same apparatus.

In some examples, an apparatus in accordance with the disclosure may beused to process and pitch densify a wide range of carbon fiber materialsto fabricate a C—C composite component. For example, as noted above, anapparatus may be configured to process and pitch densify apre-carbonized carbon fiber material. A pre-carbonized carbon fibermaterial may be a fiber material that has undergone carbonization toremove non-carbon elements prior to being inserted in an apparatus forcompression and pitch densification. The use of a pre-carbonized carbonfiber material may eliminate carbonization processing such as, e.g., acarbonization step performed during fabrication of a preform, that mayotherwise be performed during the fabrication of a C—C compositecomponent.

In some instances, a carbon fiber material that is processed on anexample apparatus in accordance with the disclosure does not require aseparate binder material to hold the different fibers of the carbonfiber material together. Instead, such an example apparatus may addmelted pitch a carbon fiber material the does not include a separatebinder material. The pitch may both increase the density of the material(densify the material) and bind the different fibers of the materialtogether. In this manner, the pitch material may serve to both densifyand bind the compressed material together with in the mold cavity.

Example apparatus features and carbon fiber materials will be describedin greater detail with reference to FIGS. 2-6. An associated exampletechnique is described below with reference to FIG. 7. However, anexample aircraft brake assembly that may include one or more C—Ccomposite materials manufactured in accordance with examples of thisdisclosure will first be described with reference to FIG. 1.

FIG. 1 is a conceptual diagram illustrating an example assembly that mayinclude one or more C—C composite material components formed inaccordance with the techniques of this disclosure. In particular, FIG. 1illustrates an aircraft brake assembly 10, which includes wheel 12,actuator assembly 14, brake stack 16, and axle 18. Wheel 12 includeswheel hub 20, wheel outrigger flange 22, bead seats 24A and 24B, lugbolt 26, and lug nut 28. Actuator assembly 14 includes actuator housing30, actuator housing bolt 32, and ram (not labeled). Brake stack 16includes alternating rotor discs 36 and stators 38, which move relativeto each other. Rotor discs 36 are mounted to wheel 12, and in particularwheel hub 20, by beam keys 40. Stator discs are mounted to axle 18, andin particular torque tube 42, by splines 44. Wheel assembly 10 maysupport any variety of private, commercial, or military aircraft.

Wheel assembly 10 includes wheel 18, which in the example of FIG. 1 isdefined by a wheel hub 20 and a wheel outrigger flange 22. Wheeloutrigger flange 22 is mechanically affixed to wheel hub 20 by lug bolts26 and lug nuts 28. Wheel 12 defines bead seals 24A and 24B. Duringassembly, an inflatable tire (not shown) may be placed over wheel hub 20and secured on an opposite side by wheel outrigger flange 22.Thereafter, lug nuts 28 can be tightened on lug bolts 26, and theinflatable tire can be inflated with bead seals 24A and 24B providing ahermetic seal for the inflatable tire.

Wheel assembly 10 may be mounted to an aircraft via torque tube 42 andaxle 18. In the example of FIG. 1, torque tube 42 is affixed to axle 18by a plurality of bolts 46. Torque tube 42 supports actuator assembly 14and stators 38. Axle 18 may be mounted on a strut of a landing gear (notshown) to connect wheel assembly 10 to an aircraft.

During operation of the aircraft, braking may be necessary from time totime, such as during landing and taxiing. Accordingly, wheel assembly 10may support braking through actuator assembly 14 and brake stack 16.Actuator assembly 14 includes actuator housing 30 and ram 34. Actuatorassembly 14 may include different types of actuators such as, e.g., anelectrical-mechanical actuator, a hydraulic actuator, a pneumaticactuator, or the like. During operation, ram 34 may extend away fromactuator housing 30 to axially compress brake stack 16 againstcompression point 48 for braking.

Brake stack 16 includes alternating rotor discs 36 and stator discs 38.Rotor discs 36 are mounted to wheel hub 20 for common rotation by beamkeys 40. Stator discs 38 are mounted to torque tube 42 for commonrotation by splines 44. In the example of FIG. 1, brake stack 16includes four rotors and five stators. However, a different number ofrotors and/or stators may be included in brake stack 16. Further, therelative positions of the rotors and stators may be reverse, e.g., suchthat rotor discs 36 are mounted to torque tube 42 and stator discs 38are mounted to wheel hub 20.

Rotor discs 36 and stator discs 38 may provide opposing frictionsurfaces for braking an aircraft. As kinetic energy of a moving aircraftis transferred into thermal energy in brake stack 16, temperatures mayrapidly increase in brake stack 16, e.g., beyond 200 degrees Celsius.With some aircraft, emergency braking may result in temperatures inexcess of 500 degrees Celsius, and in some cases, even beyond 800degrees Celsius. As such, rotor discs 36 and stator discs 38 that formbrake stack 16 may include robust, thermally stable materials capable ofoperating at such temperatures. In one example, rotor discs 36 andstator discs 38 are formed of a metal alloy such as, e.g., a super alloybased on Ni, Co, Fe, or the like.

In another example, rotor discs 36 and/or stator discs 38 are formed ofa C—C composite material fabricated according to one or more exampletechniques of this disclosure. In particular, at least one of rotordiscs 36 and/or at least one of stator discs 38 may be formed from acarbon-based fiber material fabricated using a pitch densificationapparatus, where the apparatus is configured to receive a carbon fibermaterial in a mold cavity, compress the carbon fiber material in themold cavity, and impregnate the processed carbon fiber material withpitch to densify the material in the mold cavity. From this compressedand densified carbon fiber material, a C—C composite component may beformed that defines a general shape of a rotor disc or stator disc.

Independent of the specific material chosen, rotor discs 36 and statordiscs 38 may be formed of the same materials or different materials. Forexample, wheel assembly 10 may includes metal rotor discs 36 and C—Ccomposite stator discs 38, or vice versa. Further, each disc of therotor discs 36 and/or each disc of the stator discs 38 may be formed ofthe same materials or at least one disc of rotor discs 36 and/or statordiscs 38 may be formed of a different material than at least one otherdisc of the rotor discs 36 and/or stator discs 38.

As noted, rotor discs 36 and stator discs 38 may be mounted in wheelassembly 10 by beam keys 40 and splines 44, respectively. Beam keys 42may be circumferentially spaced about an inner portion of wheel hub 20.Beam keys may be shaped with opposing ends (e.g., opposite sides of arectangular) and may have one end mechanically affixed to an innerportion of wheel hub 20 and an opposite end mechanically affixed to anouter portion of wheel hub 20. Beam keys 42 may be integrally formedwith wheel hub 20 or may be separate from and mechanically affixed towheel hub 20, e.g., to provide a thermal barrier between rotor discs 36and wheel hub 20. Toward that end, in different examples, wheel assembly10 may include a heat shield (not shown) that extends out radially andoutwardly surrounds brake stack 16, e.g., to limit thermal transferbetween brake stack 16 and wheel 12.

Splines 44 may be circumferentially spaced about an outer portion oftorque tube 42. Splines 44 may be integrally formed with torque tube 42or may be separate from and mechanically affixed to torque tube 42. Insome examples, splines 44 may define lateral grooves in torque tube 42.As such, stator discs 38 may include a plurality of radially inwardlydisposed notches configured to be inserted into a spline.

Because beam keys 40 and splines 44 may be in thermal contact with rotordiscs 36 and stator discs 38, respectively, beam keys 40 and/or splines44 may be made of thermally stable materials including, e.g., thosematerials discussed above with respect to rotor discs 36 and statordiscs 38. Accordingly, in some examples, example techniques of thedisclosure may be used to form a beam key and/or spline for wheelassembly 10. For example, a pitch densification apparatus, such as,e.g., apparatus 50 (FIG. 2), that is configured receive a carbon fibermaterial, compress and/or needle the carbon fiber material, andimpregnate the compressed and/or needled carbon fiber material withpitch all within the same mold cavity, may be used to form a C—Ccomposite component having a general shape of beam key 40 and/or spline44.

FIG. 2 is a conceptual block diagram illustrating an example apparatus50. Apparatus 50 is configured to process material 52 in mold cavity 55of mold 54 and pitch densify the processed material without removingmaterial 52 from mold cavity 55 of mold 54. In particular, apparatus 50is configured to process material 52 by reducing the volume of moldcavity 55 (e.g., by adjusting the dimensions of mold cavity 55) tocompress material 52 within mold cavity 55 (represented in FIG. 2 ascompression module 58). As shown, apparatus 50 is further configured todensify material 52 via a vacuum pressure infiltration (VPI) process(represented in FIG. 2 as vacuum pressure infiltration (VPI) module 60).For example, after material 52 is compressed within mold cavity 55 ofmold 54, apparatus 50, using VPI module 60, may carry out one or morecycles of VPI to densify material 52 with pitch. Apparatus 50 mayoptionally be configured to process a material by needling or otherwiseentangling portion of material 52 within mold cavity 55 (represented inFIG. 2 as needling module 62)

In general, compression module 58, VPI module 60, and needling module 62are representative in FIG. 2 of the various structural features andcomponents in apparatus 50 that allow apparatus 50 to perform each ofthe respective processing functions. Examples of the structural featuresand components represented by compression module 58, VPI module 60, andneedling module 62 include those described herein with regard to eachrespective process.

Apparatus 50 includes mold 54, which defines mold cavity 55 that housesmaterial 52 to be compressed and densified by apparatus 50. Duringoperation of apparatus 50, compression module 58 may compress at least aportion of material 52 within mold cavity 55 by adjusting the volume ofmold cavity 55 from a first volume to a second volume less than thefirst volume. After compressing material 52 in mold cavity 55, pitch 56may be pressurized in mold cavity 55 of mold 54 to fill the pores ofmaterial 52. Apparatus 50 may pressurize the pitch in mold cavity 55using VPI module 60. In this manner, apparatus 50 may be used tocompress material 52 and to increase the density of the processedmaterial by impregnating material 52 with pitch to form a C—C compositecomponent. Optionally, prior to compressing material 52, needling module62 may needle material 52 by retractably extending one or more needlesinto at least a portion of mold cavity 55 during operation of apparatus50 to entangle material 52.

Mold 54 may include different ports for receiving pitch 56 (e.g., froman external apparatus for supplying pitch to mold cavity 55), ventingair forced out of the pores of material 52 by pitch 56 duringdensification within mold cavity 55, receiving pressurized gas,evacuating gas to create a vacuum pressure in mold cavity 55, or thelike. During operation of apparatus 50, mold cavity 55 of mold 54 mayconstrain material 52 by providing a bounded cavity for holdingpressurized pitch 56. In some examples, mold 54 may be separate from andinsertable into apparatus 50. In other examples, mold 54 may be apermanent part of apparatus 50.

While mold 54 is shown in FIG. 2 as defining a single mold cavity 55 forreceiving material 52, in other examples, mold 52 may define a pluralityof mold cavities each configured to receive a carbon material. In someexamples, mold cavity 55 has a shape corresponding to a shape of afinished C—C composite component. For example, mold cavity 55 may have ashape substantially corresponding to a shape of an annular rotor disc oran annular stator disc (e.g., rotor disc 36 or stator disc 28 in FIG.1). During processing within mold cavity 55 (e.g., after beingcompressed within mold cavity), material 52 may assume the shape of moldcavity 52 such that material 52 substantially corresponding to thefinished component. In some examples, material 52 may optionally bemachined to arrive at a desired shape.

As will be described in greater detail below with reference to FIGS. 4and 5, mold 54 may include one or more features that are moveable suchthat the volume of mold cavity 55 may be adjusted during operation ofcompression module 58, e.g., by adjusting the dimensions of mold cavity55. In one example, mold cavity 55 of mold 54 may be defined in part bytop and bottom surfaces of mold 54. Compression module 58 may actuatethe top surface of mold 54 and/or bottom surface of mold 54 relative toone another to reduce the volume of mold cavity 55. Depending on thevolume of material 52, material 52 may be compressed in mold cavity 55as compression module 58 actuates the top surface of mold 54 and/or thebottom surface of mold 54. In this manner, material 52 may be compressedin the mold cavity 55 by apparatus 50 to a desired fiber volume.

Apparatus 50 may be capable of processing a variety of differentmaterials. In general, C—C composite components fabricated usingapparatus 50 include carbon materials reinforced in a carbon matrix.Accordingly, material 52 may include, but is not limited to, woven andnon-woven carbon-based fiber materials. The carbon-based fiber materialsmay, in some examples, be a continuous roving or continuous TOWmaterials. In some examples, the carbon-based fiber materials mayinclude polyacrylonitrile (PAN) fibers. In other examples, thecarbon-based fiber materials may include a pitch fiber, where the carbonfiber materials are fabricated from pitch material. Other types offibers may also be used such as, e.g., carbonized rayon fibers andcellulose fibers.

Prior to being inserted into apparatus 50, material 52 may undergoprocessing to prepare the material for forming a C—C compositecomponent. For example, material 52 may be carbonized prior to insertingmaterial 52 into apparatus 50 to remove non-carbon elements (e.g., H, N,O, S, or the like) and other impurities from the carbon fiber material.Such a material may be referred to as a pre-carbonized material.Pre-carbonized materials that may be utilized include carbonized PANfibers, carbonized pitch fiber, and carbonized rayon fibers.

In instances when material 52 is pre-carbonized, material 52 may bepartially carbonized or fully carbonized prior to being place withinmold cavity 55. In some examples, a fully carbonized material mayexhibit a density between approximately 1.74 grams per cubic centimeterand approximately 1.78 grams per cubic centimeter, although other valuesare contemplated. By inserting a fully carbonized material into moldcavity 55 of apparatus 50, a separate carbonization processing step suchas, e.g., a carbonization step performed during preform fabrication, maybe eliminated during the fabrication of a C—C composite component.

In additional examples, as described further with reference to FIGS. 3Aand 3B, material 52 may initially include a plurality of segmentslayered on one another within mold cavity 55. Each segment of material52 may be formed, for example, from a knitted, woven, and/or non-wovenmaterial. In some examples, a portion of the material may be needledtogether to define a segment. In some additional examples, a binder maybe added to a portion of the material define a segment. For example, abinder such as, e.g., polyvinyl acetate or starch may be added toportion of material.

In some examples, a C—C composite material formed from layered segmentsof material 52 using apparatus 50 may exhibit increased mechanicalstrength compared to a C—C composite not formed from a plurality oflayered segment. In some examples, using a plurality of layer segmentsto initially form material 52 may allow material 52 to withstand theforce of pressurized pitch during a pitch densification cycle onapparatus 50 without shearing apart.

Apparatus 50 may be used to increase the density of material 52 withinmold cavity 55. When initially inserted into mold cavity 55 of mold 54,material 52 may exhibit a relatively low fiber density (e.g., mass offiber/volume of fiber) as compared to a finished C—C compositecomponent. For example, material 52 may exhibit a fiber density betweenapproximately 0.25 grams per cubic centimeter (g/cc) and approximately1.75 g/cc before being inserted into mold cavity 55 for processing byapparatus 50. Finished C—C composite components (e.g., materials thathave been compressed via compression module 58 and densified with pitchvia VPI module 60), on the other hand, generally exhibit higherdensities. In some examples, a finished C—C composite component mayexhibit a density greater than 1.5 grams per cubic centimeter, such as,e.g., a density greater than 1.75 grams per cubic centimeter. Thedensity of the C—C composite component may affect the performance of thecomponent during subsequent operation such as, e.g., the ability of thecomponent to withstand shear forces and thermal cycling. The increase indensity may be attributed at least in part to the compression and pitchdensification of material 52 after initially being inserted into moldcavity 55 of apparatus 50.

In some examples, after material 52 is inserted into mold cavity,compression module 58 may reduce the volume the dimensions of moldcavity (e.g., by changing the dimensions of mold cavity 55) to compressmaterial 52, e.g., to increase the density of material 52 from that ofthe original density of material 52 when first placed in mold cavity 55.In some examples, compression module 58 may include a hydraulic press orother press (not shown in FIG. 2) for compressing material 52 in moldcavity 55 of mold 54 to increase the density of material 52. Duringoperation, such press may apply a mechanical force to material 52 withinmold cavity 55 of mold 54 to reduce the volume of material 52. Forexample, the press of compression module 58 may apply a mechanical forceto material 52 by actuating or “pressing” two more separate surfaces ofmold 54 together in a manner that reduces the volume of mold cavity 55.The mechanical force applied by compression module 58 may increase thepacking density of material 52 by reducing the volume of mold cavity 55.As the volume of cavity 55 decreases, the volume of space occupied bymaterial 52 increases, thereby increasing the fiber volume density ofmaterial 52 within cavity. In various examples, the press of compressionmodule 58 may include a pneumatic cylinder, a hydraulic cylinder, or yetanother mechanical actuating force such as, e.g., a ball and screwarrangement, used to compress material 52 in mold cavity 55.

Compression module 58 may compress material 52 to any suitable density.In some examples, compression module 58 may compact material 52 to afiber volume density between approximately 15 volume percent materialand approximately 50 volume percent material such as, e.g., betweenapproximately 17 volume percent material and approximately 30 volumepercent material. The fiber volume density may be calculated by dividingthe amount of space occupied by the fibers of material 52 by the totalamount of space occupied by material 52 (including air between thedifferent fibers of material 52).

The amount of force applied to material 52 using compression module 58may vary, e.g., based on the type of material 52 being used and the typeof C—C composite component to be fabricated. That being said, in someexamples, compression module 58 may be used to apply at leastapproximately 1.9 pounds per square inch (psi) to material 52 whencompressing material 52 in mold cavity 55 with compression module 58.Other values are both possible and contemplated.

As noted above, in addition to or in lieu of processing material 52using compression module 58, material 52 may be needled within moldcavity 55 of mold 54 using needling module 62 to entangle all or portionof material 52. Needling module 62 may include a single needle or aplurality of needles (e.g., two, three, four, or more) used to needlematerial 52. During operation, the needle(s) of needling module 62 mayretractably extend into at least a portion of mold cavity 55 of mold 54and through material 52. In some examples, one or more of the needles ofneedling module 62 may have a hooked distal end that extends into atleast a portion of mold cavity 55 and through material 52. Upon beingrefracted, needles 62 may hook and/or entangle different fibers ofmaterial 52 on a downward stoke.

Needling may be useful to increase the mechanical strength of material52 within mold cavity 55 prior to pitch densifying material 52 withinmold cavity 55. For example, in instances where material 52 includesmultiple different fibers that are randomly oriented or unconnected withrespect to each other, the different fibers of material 52 may becomeseparated from one another during pitch densification. This may reducethe strength of a resulting C—C composite component. However, byneedling material 52 within mold cavity 55 with needles 62, material 52may be entangled into a structure that resists separation duringsubsequent pitch densification. In some examples, such needling ofcarbon material may increase the number of fibers oriented in thez-direction (e.g., as labeled in FIG. 5).

Although apparatus 50 in the example of FIG. 2 includes needling module62, apparatus 50 may compress material 52 within mold cavity 55 viacompression module 58 and subsequently pitch densifying the compressedmaterial within mold cavity 55 without needling material 52. Forexample, in situations where material 52 includes fibers that are toobrittle or otherwise unsuitable for needling, apparatus 50 maynevertheless compress the carbon-fiber material and pitch densify thematerial within mold cavity 55. Accordingly, in some examples, apparatus50 may not include needling module 62.

In examples where material 52 is needled in apparatus 50 by needlingmodule 62, apparatus 50 may needle material 52 before or after material52 is compressed by compression module 58. In some examples, needlingmaterial 52 before material 52 is compressed by compression module 58may be useful because the material is less dense. A less dense material52 may be more readily penetrated by needles 62 during needling than amore dense material 52 such as, e.g., a material that has beencompressed by compression module 58 with mold cavity 55.

Independent of the specific processing steps performed on material 52 inmold cavity 55 prior to pitch densification, apparatus 50 may pitchdensify material 52 by impregnating material 52 with pitch 56, e.g.,using VPI module 60. Pitch 56 may be a hydrocarbon-rich material thatmay be extracted, e.g., from coal, tar, and petroleum. Pitch 56 may alsobe synthetically produced. In different examples, pitch 56 may come froma single source (e.g., coal) or may be a combination of differentpitches from different sources. In some examples, pitch 56 may be amesophase pitch. In other examples, pitch 56 may be an isotropic pitch.Combinations of mesophase and isotropic pitches are also contemplated.

Pitch 56 may have a melting temperature greater than typical ambienttemperatures. As such, pitch 56 may be heated to a flowable state priorto densification of material 52. In some examples, as described ingreater detail below with respect to FIGS. 6A and 6B, pitch 56 may beadded to apparatus 50 in a solid state and then heated above the meltingtemperature in apparatus 50 during densification. In other examples,pitch 56 may be heated above the melting temperature separately fromapparatus 50 and conveyed to mold cavity 55 of apparatus 50 as a meltedpitch. In some examples, pitch 56 may be heated to a temperature betweenapproximately 200 degrees Celsius and approximately 450 degrees Celsiussuch as, e.g., between approximately 275 degrees Celsius andapproximately 330 degrees Celsius to melt into a flowable state.

Apparatus 50 in the example of FIG. 2 may densify material 52 in moldcavity 55 with pitch 56 using at least one cycle of VPI via VPI module58. During a VPI cycle, mold cavity 55 may be reduced to vacuum pressureto evacuate the pores of material 52. In some examples, a vacuumpressure between approximately 1 torr and approximately 100 torr, suchas, e.g., between approximately 10 torr and approximately 20 torr may becreated. With the pores of material 52 ready to receive pitch 56, moldcavity 55 may be flooded with pitch 56. In examples where a portion ofsolid pitch is provided in apparatus 50, as will be described withreference to FIGS. 6A and 6B, flooding may be accomplished by heatingpitch 56 above the melting temperature of pitch 56. In examples wherepitch 56 is conveyed to apparatus 50 in a flowable state, flooding maybe accomplished, e.g., by pressurizing a tank of pitch 56, mechanicallyconveying pitch 56, or allowing a vacuum pressure in mold cavity 55 todraw pitch 56 into mold cavity 55. After flooding, a gas such as, e.g.,an inert nitrogen gas, can be used to pressurize pitch 56 in mold cavity55. In some examples, a gas pressure between approximately 10 pounds persquare inch (psi) and approximately 1000 psi, such as, e.g., betweenapproximately 300 psi and approximately 700 psi may be used.Pressurization may help pitch 56 travel through the different pores ofmaterial 52. In this manner, apparatus 50 may be used to density amaterial through one or more cycles of VPI.

In some examples, as briefly noted above, material 52 may exhibit adensity between approximately 0.25 grams per cubic centimeter (g/cc) andapproximately 1.0 g/cc after being compressed and/or needled but priorto densification. After a cycle of VPI (60), material 52 may, in someexamples, exhibit a density between approximately 1.35 grams per cubiccentimeter and approximately 1.5 grams per cubic centimeter. A cycle ofVPI carried out by VPI module 60 may be defined as a singledensification during which perform 52 is infiltrated with pitch underone defined set of conditions (e.g., gas flow rates, temperature, time,etc.).

Apparatus 50 may densify material 52 with a single cycle of VPI ormultiple cycles of VPI via VPI module 60 without removing material 52from mold cavity 55. For example, apparatus 50 may densify material 52via VPI module 60 until the material exhibits a density suitable for theC—C composite component being fabricated. In some examples, apparatus 50may densify material 52 within mold cavity 55 until the materialexhibits a density between approximately 1.6 grams per cubic centimeterand approximately 1.9 grams per cubic centimeter.

Although apparatus 50 in the example of FIG. 2 includes VPI module 60,in additional examples, apparatus 50 may be configured to densifymaterial 52 using densification techniques other than vacuum pressureinfiltration in addition to or in lieu of VPI module 60. In one example,apparatus 50 may densify material 52 in mold cavity 55 using one or moreresin transfer molding (RTM) cycles. In general, a resin transfermolding cycle may involve actuating a ram (e.g., a hydraulic piston)through a cavity filled with pitch 56 to inject pressurized pitch intomold cavity 55 and through the different pores of material 52. Inanother example, apparatus 50 may densify material 52 using one or morevacuum-assisted resin transfer molding (VRTM) cycles. A vacuum-assistedresin transfer molding cycle may be considered a form of a RTM cycle inwhich a vacuum pressure is created in mold cavity 55 at least prior tothe beginning of the RTM cycle. An example apparatus configured to pitchdensify a material according to a selectable one of a plurality ofdifferent pitch densification techniques is described incommonly-assigned U.S. patent application Ser. Nos. 12/938,170 and12/938,201, both entitled “APPARATUS FOR PITCH DENSIFICATION” which werefiled on Nov. 2, 2010. The entire contents of both these applicationsare incorporated herein by reference.

While apparatus 50 may be configured to pitch densify material 52 usingdifferent pitch densification techniques in addition or in lieu of VPIcycle using VPI module 60, a VPI cycle may be comparatively gentler onmaterial 52 than other types of densification cycles. Without beingbound by any particular theory, it is believed that as pitch 56initially infiltrates material 52, a pressure gradient is created acrossmaterial 52. The pressure gradient causes internal stresses withinmaterial 52. If material 52 is not strong enough to accommodate theinternal stresses, sections of material 52 may shear apart or differentlayers of material 52 may delaminate, destroying the shape andmechanical strength of material 52. This effect may be exacerbated whenmaterial 52 is not first processed into a preform, as according to someexamples of the disclosure. However, by creating a vacuum pressure inmold cavity 55 at the beginning of a VPI cycle, backpressure inhibitingthe free flow of pitch 56 into the different pores of material 52 may bereduced or eliminated. Further, the pressure applied on material 52during the pressurization part of VPI cycle may be lower than thepressure applied on material 52 during other types of densificationtechniques such as, e.g., a RTM cycle. In this regard, VPI cycle may beuseful for pitch densifing materials that are not first processed intopreforms.

Apparatus 50 may be used to process materials that exhibit differentsizes and shapes. The size and shape of the materials may vary, e.g.,based on the size and shape of mold cavity 55 and the size and shape ofthe C—C composite component being fabricated. However, in some examples,material 52 may be processed to define a shape substantiallycorresponding to a shape of a finished component before being insertedinto mold 54 of apparatus 50. In some additional examples, material 52may be processed into one or more discrete segments before beinginserted into mold 54 of apparatus 50. Processing material 52 intodiscrete segments may add mechanical strength to material 52 and mayhelp facilitate placement of material 52 into apparatus 50.

FIGS. 3A and 3B are schematic drawings of example segments of material52 that may be inserted into apparatus 50 for processing and subsequentpitch densification. FIG. 3A illustrates an example individual segmentof carbon material 81 (also referred to as “individual segment 81”) thatis fabricated from material 52 and that is configured (e.g., size andshaped) to be inserted into mold cavity 55 of mold 54. FIG. 3Billustrates a plurality of segments 80A-80E of material (collectivelyreferred to as “segments 80”) that are fabricated from material 52 andthat together define a shape generally corresponding to a shape of afinished C—C composite component, which in the example of FIG. 3B is abrake disc rotor or brake disc stator. Each of segments 80 (FIG. 3B) maybe the same or substantially similar to that of individual segment 81(FIG. 3A).

Segments 80 may be fabricated using any suitable technique. In oneexample, a portion of material (e.g., a knitted, woven, or non-wovenmaterial) may be precut or otherwise preprocessed into a desired shapefor insertion into cavity 55 of mold 54. Example of individual segmentsformed form non-woven material may include needled fibers, materialswith binders such as polyvinyl acetate (PVA) or starch, binder fibers(such as polypropylene, polyethylene), air entangled material, and waterjet entangled materials.

While the disclosure is not limited to segments 80 having any particulardimensions, in some examples, each of segments 80 may be sized andshaped to generally correspond to a size and shape of a finished C—Ccomposite component (or portion thereof) when assembled in mold cavity55. In one example, a finished component may be a brake rotor disc or abrake stator disc that defines a substantially annular shape (e.g.,rotor disc 36 or stators disc 38 in aircraft brake assembly 10 of FIG.1). In such an example, segments 80 may be sized and shaped tosubstantially correspond to a size and shape of rotor disc 36 or statorsdisc 38 when segments 80 are assembled. In some examples, segments 80 inthe example of FIG. 3B combine together to define an annular shape thathas an inner diameter 82 and an outer diameter 84. In some examples,inner diameter 82 may range between approximately 6 inches andapproximately 13 inches, while outer diameter 84 may range betweenapproximately 9 inches and approximately 25 inches. However, othervalues are both possible and contemplated.

Segment 81 may define any suitable shape. In examples where segment 81is used in combination with other segments to define an annular shape,segment 80 may define a lesser portion of an annulus. For example,segment 81 may define a generally trapezoidal shape with arcuate bases.In additional examples where segment 81 is used in combination withother segments, each segment may be design to overlap with anothersegment when placed in mold cavity 55 of mold 54. Overlapping differentsegments of material 52 in mold cavity 55 may create an interlockedstructure that resists separation during pitch densification.

Segment 80 in the example of FIG. 3A defines a thickness in theZ-direction indicated on FIG. 3A. Apparatus 50 may be capable ofcompressing and/or needling and pitch densifying segments 80 of material52 that has any suitable thickness. One or multiple layers of segments80 may be used to form the thickness of material 52. In some examples,the overall thickness of material 52 suitable for forming a C—Ccomposite component. In these examples, the overall thickness ofmaterial 52 may range between approximately 0.25 inches andapproximately 2 inches, although other values are possible. In examples,in which multiple overlapping layers of segments form material 52, thethickness of the individual segments may range between approximately0.05 inches and approximately 0.20 inches. While the foregoingdescription included example shapes and dimensions for material 52, isshould be appreciated that other shapes and dimensions are contemplatedand that the disclosure is not limited to using a material that has anyparticular size or that defines any particular shape.

As noted with reference to FIG. 2, mold 54 is configured to receivematerial 52 within mold cavity 55. The specific shape and size of moldcavity 55 may vary, e.g., based on the shape and size of the C—Ccomposite component to be formed by apparatus 50. FIGS. 4 and 5illustrate different example views of one example of mold 54 inaccordance with the disclosure. FIGS. 4A and 4B are conceptual diagramsillustrating a first portion 90 and second portion 92, respectively,that define mold cavity 55. FIG. 5 is a conceptual diagram illustratingan example mold cavity 55 defined at least in part by the first andsecond portions 90, 92 of FIGS. 4A and 4B, respectively.

In the example of FIGS. 4 and 5, mold cavity 55 is defined by generallyopposing surfaces of first portion 90 and second portion 92. Firstportion 90 and second portion 92 are separable at parting line 94, e.g.,to open mold 54 for adding or removing material 52. First portion 90defines a top surface 96, and second portion 92 defines a bottom surface98 opposite top surface 96. In general, mold cavity 55 may be configuredto receive material 52. For example, in operation, material 52 may beplaced in mold cavity 55 on bottom surface 98 and then first portion 90may be placed over material 52. First portion 90 and second portion 92may be moved relative to each other (e.g., by press of compressionmodule 58 (FIG. 2)) to compress material 52 within mold cavity 55. Uponcompressing material 52 in mold cavity 55 of mold 54, mold 54 may definea bounded area for pitch densifying material 52.

During the operation of apparatus 50, the pressure in mold cavity 55 maybe varied from vacuum pressure to above ambient pressure, pitch 56 mayadded to mold cavity 55, and air in the pores of material 52 may bevented during densification. To provide fluid communication forprocessing material 52, mold 54 may include different fluid access portsto cavity 55. In the example of FIG. 5, mold 54 includes pitch port 102,pressure port 104, and vent ports 106. Pitch port 102 may be in fluidcommunication with a pitch source for supplying melted pitch 56 to moldcavity 55 during a pitch densification cycle. Pressure port 104 may bein fluid communication with a gas source to adjust the pressure withinmold cavity 55 during a VPI cycle. Vent ports 106 may be in fluidcommunication with a vacuum source to create a vacuum pressure in moldcavity 55 during a VPI cycle or a venting line to vent air from material52 within mold cavity 55 as melted pitch infiltrates the pores ofmaterial 52.

As noted above, apparatus 50 may be capable of needling material 52 inmold cavity 54 via needling module 62. During needling operation,needle(s) may retractably extend into at least a portion of mold cavity55 of mold 54 and through at least a portion of material 52 to entangledifferent fibers of material 52. To accommodate needling in theseexamples, mold 54 may include needle apertures 108. Needle apertures 108define openings that allow needles to retractably extend into moldcavity 55. Needle apertures 108 may extend through first portion 90 ofmold 54, second portion 92 of mold 54, or both first portion 90 andsecond portion 92 of mold 54, although in the example of FIGS. 4 and 5,needle apertures 108 extend through second portion 92 of mold 54. Mold54 may include a single needle aperture 108 or a plurality (e.g., two,three, four, or more) of needle apertures 108. In some examples, mold 54may include between approximately 5 needle apertures per square inch andapproximately 10 needle apertures per square inch.

As noted above, during the operation of apparatus 50, material 52 may becompressed in mold cavity 55 of mold 54 using compression module 58(FIG. 2). In some examples, a press may actuate first portion 90relative to second portion 92 in the Z-direction (as indicated in FIG.5) to reduce the volume of mold cavity 55 and compress material 52 inmold cavity 55. During such an operation, top surface 96 and bottomsurface 98 may directly or indirectly contact material 52 to compressmaterial 52 in mold 54

In some examples, first portion 90 may define a recess 110 that projectsinto the plane of top surface 96, and second portion 92 may define amated protrusion 99 extending out of the plane of bottom surface 98.Recess 110 may be sized and shaped such that recess 110 mates withprotrusion 99 when first portion 90 of mold 54 is actuated againstsecond portion 92 to reduce the volume of mold cavity 55 and/or sealmold cavity 55. In other examples, first portion 90 may define asubstantially planar top surface 96 that mates with protrusion 99 ofsecond portion 92 when first portion 90 of mold 54 is moved relative tosecond portion 92 of mold 54 to seal mold cavity 55. In general,although mold 54 in the example of FIG. 5 includes recess 110 andprotrusion 99, it shall be appreciated that the disclosure is notlimited in this respect, and in other examples, the techniques of thedisclosure may be implemented with mold configurations other than thosedescribed herein.

As seen in FIG. 5, in some examples, material 52 in mold cavity 55 maybe compressed by reducing the Z-direction thickness 112 of material 52within mold cavity 55. During compression, the fiber volume density ofmaterial 52 may increase within mold cavity 55 as air is removed frombetween the different fibers of material 52. For example, aftercompression, material 52 may exhibit a fiber volume density betweenapproximately 15 percent and approximately 50 percent such as, e.g.,between approximately 24 percent and approximately 28 percent, where thefiber volume density may be calculated by dividing the amount of spaceoccupied by the fibers of material 52 by the total amount of spaceoccupied by material 52 (including air between the different fibers ofmaterial 52). It should be appreciated, however, that the foregoingvalues are merely examples, and an apparatus in accordance with thedisclosure may compress material 52 to densities other than thoseindicated above.

FIGS. 6A and 6B are conceptual drawings illustrating an example pitchdensification apparatus 150. Pitch densification apparatus 150 isconfigured to receive a carbon fiber material within mold cavity 202,compress the carbon fiber material, and densify the compressed carbonfiber material with pitch. Although apparatus 150 does not includefeatures corresponding to needling module 62 (FIG. 2), apparatus 150 isotherwise an example of apparatus 50 (FIG. 2) and illustrates variouscomponents that may be included in apparatus 50. FIG. 6A is a conceptualdiagram illustrating apparatus 150 with mold cavity 202 in an openposition. While in an open position, material 52 may be inserted intomold cavity 202 or material 52 may be removed from mold cavity 202 afterit has been compressed and/or densified. FIG. 6B is a conceptual diagramillustrating apparatus 150 with mold cavity 202 in a closed position.While in a closed position, material 52 in mold cavity 202 may bedensified with pitch, e.g., after material 202 has been compressedwithin mold cavity 202.

As shown, apparatus 150 includes press platen 152A and 152B, bolster154, clamp plates 156A and 156B, backing plate 158, insulating plates160A and 160B, bolster ejector plate 162, ejector pins 164, vacuum linecontrol cylinder 166, vacuum line control rod 168, vacuum port 170, gasfeed control cylinder 172, gas control rod 174, gas port 176, pitchchamber 178, pitch feed cylinder 180, and pitch feed ram 181. Mold 200is interposed between insulating plates 160A and 160B. Mold 200 definesmold cavity 202, which houses material 52.

In general, press platens 152A and 152B move relative to one another tocompress material 52 in mold cavity 202 of mold 200. During operation,press platens 152A and 152B apply pressure from opposing directions toconstrain material 52 in mold cavity 202. One or both of press platens152A and 152B may be connected to a mechanical actuating feature (notshown) such as, e.g., a pneumatic cylinder, a hydraulic cylinder, a balland screw arrangement, or the like. As such, one or both of pressplatens 152A and 152B may move in the Z-direction illustrated in FIGS.6A and 6B to allow mold 200 to open at a mold parting line sealed bymold parting seal 194, e.g., to insert or remove material 52 from moldcavity 202 of mold 200. Press platens 152A and 152B may be intergrallyformed (i.e., permanently connected) with other features of apparatus150, or press platens 152A and 152B may be separate features, asillustrated in FIGS. 6A and 6B. In other words, press platens 152A and152B may be purpose-built or may be part of a standard press to whichother components of apparatus 150 are added.

Press platen 152A and 152B are connected to bolster 154 and clamp plate156B, respectively. In turn, bolster 154 is connected to clamp plate156A, while clamp plate 156B is connected to bolster ejector plate 162.In general, bolster 154 and bolster ejector plate 162 may function todefine cavities for receiving and housing various features of apparatus150. For example, bolster 154 defines pitch chamber 178 and bolsterejector plate 162 defines cavities to receive ejector pins 164. Bolster154 and bolster ejector plate 162 may protect the various features fromthe pressing force of press platens 152A and 152B during operation ofapparatus 150.

Clamp plates 156A is interposed between bolster 154 and backing plate158. Clamp plate 156B, by contrast, is interposed between bolsterejector plate 162 and insulating plate 160B. Clamp plates 156A and 156Bfunction to clamp different features of apparatus 150 from moving out ofalignment.

Apparatus 150 includes backing plate 158 interposed between clamp plate158A and insulating plate 160A. Backing plate 158 defines cavities forreceiving and housing various features of apparatus 150. For example,backing plate 110 defines pitch chamber 178, as well as cavities toreceive vacuum line control cylinder 166, vacuum line control rod 168,gas feed control cylinder 172, and gas control rod 174. Backing plate158 may protect the different features from the pressing force of pressplatens 152A and 152B during operation of apparatus 150.

Mold 200 is located between insulating plates 160A and 160B. Insulatingplates 160A and 160B may limit thermal transfer away from mold 200,e.g., to help mold 200 retain heat during pitch densification.Accordingly, insulating plates 160A and 160B may, in some examples, beformed from a low thermal conductivity material. To further limitthermal transfer away from mold 200, connection lines extending betweenmold 200 and other features of apparatus 150 may, in some examples, beprovided with insulating seals 184, as shown in FIGS. 6A and 6B.Insulating seals 184 may prevent thermal transfer through openings ininsulating plates 160A and 160B.

Similar to that of mold 54 (FIG. 2), mold 200 defines one or more moldcavities 202 that receive material 52 to be compressed and pitchdensified using apparatus 150. Mold 200 may be formed of soft toolingmaterials such as, e.g., a polyester or an epoxy polymer. Alternatively,mold 200 may be formed of hard tooling materials such as, e.g., cast ormachined aluminum, nickel, steel, titanium, or the like. Mold 200 maydefine different channels for conveying pitch, venting air, drawing avacuum, receiving pressurized gas, or the like to mold cavity 200.

During one or more pitch densification cycles, a vacuum pressure may becreated in mold cavity 202 for at least part of the densification cycle.Accordingly, apparatus 150 may include vacuum hardware connectable to avacuum source to create a vacuum pressure in mold cavity 202. In theexample of FIGS. 6A and 6B, vacuum hardware is provided by vacuum linecontrol cylinder 166, vacuum line control rod 168, and vacuum port 170.Vacuum port 170 provides a connection point between vacuum source 186,which is operable to create a vacuum in mold 200, and in particular moldcavity 202, that contains material 52. Vacuum line control cylinder 166is connected to vacuum line control rod 168. In operation, vacuum linecontrol rod 168 may be controllably actuated in the Z-direction shown onFIGS. 6A and 6B to selectively place vacuum source 186 in pressurecommunication with mold cavity 202, thereby controlling a vacuumpressure created in mold cavity 202. In different examples, vacuum linecontrol cylinder 166 may be a single acting cylinder, which uses acompressible fluid to actuate vacuum line control rod 168 in onedirection and a spring to return vacuum line control rod 168 to a returnposition, or a double acting cylinder, which uses a compressible fluidto both extend and return vacuum line control rod 168. In differentassemblies according to the disclosure different vacuum control hardwaremay be used, and the disclosure is not limited in this respect.

From time to time, a pressurized gas may be applied to pitch in moldcavity 202 to help densify material 52, e.g., during a VPI cycle. Tocontrol the pressurized gas, apparatus 150 may include gas controlhardware connected to a pressurized gas source. In the example of FIG.6A, for instance, apparatus 150 includes gas feed control cylinder 172,gas control rod 174, and gas port 176. Gas port 176 connects gas source188, which supplies pressurized gas, to mold cavity 202 that containsmaterial 52. In various examples, gas source 188 may be a source ofpressurized inert gas including, but not limited to, nitrogen, helium,argon, carbon dioxide, or the like. Gas control rod 174 is connected togas feed control cylinder 172. In operation, gas control rod 174 may becontrollably actuated in the Z-direction shown on FIGS. 6A and 6B toselectively place gas source 188 in fluid communication with mold cavity202, thereby controlling a gas pressure created in mold cavity 202. Indifferent examples, gas feed control cylinder 172 may be a single actingcylinder or a double acting cylinder, as discussed above with respect tovacuum line control cylinder 166. Further, as similarly discussed abovewith respect to the vacuum control hardware in apparatus 150, indifferent assemblies according to the disclosure, different features maybe used to control pressurized gas flow to mold cavity 202, and thedisclosure is not limited in this respect.

In the example of FIGS. 6A and 6B, melted pitch is supplied to moldcavity 202 from pitch chamber 178 through pitch port 204. Pitch chamber178 is thermally connected to heating source 190. In operation ofapparatus 150, a portion of solid pitch material may be inserted intopitch chamber 178. Heating source 190 may thereafter melt the portion ofsolid pitch into a flowable state in pitch chamber 178. In someexamples, heating source 190 may include a thermal transfer agent thatis passed through a tube thermally connected to pitch chamber 178 (e.g.,similar to a heat exchanger). The thermal transfer agent may be heatedin apparatus 150 or conveyed to apparatus 150 (e.g., from an externalfurnace, heat exchange, or the like). In other examples, heating source190 may be a fired burner, an electrical resistance heater, a radiofrequency (e.g., microwave) heater, or the like. In still otherexamples, heat source 190 may be a convection heating source, anelectromagnetic induction heating source, or an infrared heating source.

To control pitch delivery to mold cavity 202, apparatus 150 may alsoinclude pitch flow control features. For example, apparatus 150 includespitch feed cylinder 180 and pitch feed ram 181. Pitch feed cylinder 180is mechanically connected to pitch feed ram 181. In operation, pitchfeed cylinder 180 may controllably actuate pitch feed ram 181 in theZ-direction shown on FIGS. 6A and 6B into pitch chamber 178. In thismanner, pitch feed ram 181 may force melted pitch in pitch feed chamber178 through pitch port 204 and into mold cavity 202. In differentexamples, pitch feed cylinder 180 may be a pneumatic cylinder, ahydraulic cylinder, a ball and screw arrangement, or the like. Further,pitch feed ram 181 may be a piston, a plunger, or another device forapplying a mechanical compression force to melted pitch in pitch chamber178.

After processing and pitch densifying material 52 on apparatus 150,pressure may be released from press platens 152A and 152B to allow mold200 to be opened. In some examples, mold 200 may be removed fromapparatus 150 before opening the mold to extract a densified material.In other examples, a portion of mold 200 may be opened while mold 200resides in apparatus 150. For example, in FIGS. 6A and 6B, mold 200 maybe opened in apparatus 150 on a parting line sealed by parting seal 194.To facilitate removal of a densified material in these examples,apparatus 150 may include ejector pins 164. Ejector pins 164 may becontrollably actuated in the Z-direction shown in FIGS. 6A and 6B tohelp eject densified material from mold 200.

In operation, apparatus 200 may be used to compress material 52 in moldcavity 202 and to densify the compressed material in the same moldcavity 202 of mold 200 using a VPI cycle, as described above withrespect to apparatus 50 in FIG. 2. For example, during operation,material 52 may be inserted into mold cavity 202 of mold 200 and solidpitch may be inserted pitch chamber 178. Press platens 152A and 152B maymove relative to each other to compress material 52 in mold cavity 202and to seal mold 200 for pitch densification. Heating source 190 maymelt the solid pitch in pitch chamber 178 to a flowable state. During aVPI cycle, the pressure in mold cavity 202 may be reduced to vacuum bycontrolling vacuum line control cylinder 166 to actuate vacuum linecontrol rod 168. Upon actuating vacuum line control rod 168, mold cavity202 may be placed in pressure communication with vacuum source 186through vacuum port 170. Thereafter, pitch feed cylinder 180 may extendpitch feed ram 181 into pitch chamber 178 to force melted pitch throughpitch port 204 and into mold cavity 202. With mold cavity 202 filledwith pitch, vacuum line control cylinder 166 may control vacuum linecontrol rod 168 to close vacuum port 170. Thereafter, gas feed controlcylinder 172 may control gas control rod 174 to open gas port 176,placing mold cavity 202 housing material 52 in communication withpressurized gas source 188. In this manner, material 52 may becompressed in mold cavity 202 and thereafter pitch densified via a VPIcycle within the same mold cavity 202 of apparatus 150.

Apparatus 150, as outlined above, may include features for processing acarbon-based fiber material and pitch densifying the processed material.As shown, apparatus 150 may be a modular assembly configured to be usedwith standard press platen 152A and 152B. That is, apparatus 150 mayinclude different modular components configured to be assembled andinserted between press platens to form apparatus 150. In differentexamples, however, apparatus 150 may include different modularcomponents or non-modular components in addition to or in lieu of thecomponents illustrated and described with respect to FIGS. 6A and 6B.Therefore, although apparatus 150 includes various example components,different configuration are contemplated.

As an example of the additional or different features that may beincluded in an apparatus according to the disclosure, FIGS. 6A and 6Billustrate example thermal management features that may be included inapparatus 150 for controlling the temperature of mold 200, particularlyto control temperature of material 52 and/or pitch within mold cavity202. Because pitch is generally solid at ambient temperatures, anapparatus that includes thermal management features may help melt pitchor keep pitch in a flowable state until the pitch suitably permeates thevarious pores of material 52.

In the example of FIGS. 6A and 6B, apparatus 150 includes heater tubes192 and cooling tubes 194 for heating and cooling, respectively, mold200. Heater tubes 192 may extend through at least a portion of mold 200and be in thermal communication with mold 200. Heater tubes 192 maydefine a conduit configured for fluid communication with a thermaltransfer agent. A thermal transfer agent may include, but is not limitedto, steam, oil, a thermal transfer fluid, or the like. Heater tubes 192may be cast or machined into mold 200, or may be inserted into aperturesdefined by mold 200. Heater tubes 192 may be formed of a thermallyconductive material including, but not limited to, copper, aluminum, andalloys thereof. In operation, a thermal transfer agent may be heated inapparatus 150 or externally to apparatus 150 (e.g., in a furnace or heatexchanger) and conveyed through heater tubes 192. The heat of thethermal transfer agent may conduct through heater tubes 192, mold 200,and material 52. In this way, heater tubes 192 may conductively heatmold 200, including material 52 and pitch in mold cavity 202. In variousexamples, a thermal transfer agent may be heated to a temperaturegreater than 110 degrees Celsius such as, e.g., to a temperature betweenapproximately 285 degrees Celsius and approximately 330 degrees Celsiusduring a pitch densification cycle of apparatus 150.

After completing one or more pitch densification cycles on apparatus150, material 52 may be saturated with liquid pitch and excess pitch mayremain in mold cavity 202. To facilitate easy and rapid removal of adensified material from apparatus 150, cooling tubes 194 may be providedon apparatus 150 to cool and solidify melted pitch. In some examples,heater tubes 192 may be used as cooling tubes by conveying acomparatively cool thermal transfer agent through heater tubes 192 afterdensification. In other examples, however, apparatus 150 may includeseparate cooling tubes 194. Separate heating tubes 192 and cooling tubes194 may allow apparatus 150 to operate faster than when apparatus 150includes shared heating and cooling tubes by reducing thermal cyclingtimes.

Cooling tubes 194 may be similar to heating tubes 192 in that coolingtubes 194 may extend through at least a portion of mold 200 and may bein thermal communication with mold 200. Cooling tubes 194 may alsodefine an aperture configured for fluid communication with a thermaltransfer agent, which may be the same thermal transfer agent received byheater tubes 192 or a different thermal transfer agent. In operation,the thermal transfer agent may be conveyed through cooling tubes 194. Asa result, mold 200, including material 52 and pitch in mold cavity 202,may be conductively cooled by cooling tubes 194.

Different example material structures, molds and apparatuses have beendescribed in relation to FIGS. 2-6. FIG. 7 is a flow diagramillustrating an example method for processing a material with anapparatus configured to compress, needle, and pitch densify a material.For ease of description, the method of FIG. 7 is described as executedby apparatus 50 (FIG. 2). In other examples, however, the method of FIG.7 may be executed by apparatus 150 (FIGS. 6A and 6B) or apparatuses withdifferent configurations, as described herein.

As shown in FIG. 7, carbon fiber material 52 may be inserted into moldcavity 55 of densification apparatus 50 (250), compression module 58 maycompress material 52 in mold cavity 55 (252), and needling module 62 mayretractably extend one or more needles into at least a portion of moldcavity 55 to entangle different fibers of material 52 within the moldcavity (254). After suitably processing material 52 in mold cavity 55,apparatus 50 may then carry out one or more VPI cycles via VPI module 60to pitch densify material 52 within mold cavity 55 of mold 54 (256).

As shown in FIG. 7, material 52 may be inserted into mold cavity 55 ofmold 54 of pitch densification apparatus 50 (250). As described above,mold 54 may be removable from pitch densification apparatus 50 orpermanently formed with pitch densification apparatus 50. In someexamples, mold cavity 55 may have a shape substantially corresponding toa shape of a finished component formed from material 52. For example,mold cavity 55 may have a shape substantially corresponding to brakerotor disc 36 or brake stator disc 38 (FIG. 1). Mold 54 may be formed oftwo or more separable portions that may be separated to insert material52 into mold cavity 55. Material 52 may be a carbon-based fibermaterial, a carbon-based non-fiber material, or a non-carbon-basedmaterial. In some examples, material 52 may be pre-carbonized. In someadditional examples, material 52 may be fabricated into a plurality ofdiscrete segments that may be separately inserted into mold cavity 55.In still some additional examples, mold 54 may be preheated, e.g., to atemperature greater than 110 degrees Celsius, before inserting material52 into mold cavity 55.

Material 52 may be compressed within mold cavity 55 (252) after beinginserted into mold cavity 55 (250). Compression module 58 may apply amechanical force to material 52 to compress the material within moldcavity 55. In some examples, compression module 58 may include pressplaten or another feature that compresses material 52 in mold cavity 55,e.g., by compacting material 52 against bottom surface of the mold. Insome examples, mold 54 may include one or more features that actuate inresponse to pressure from compression module 58. Although compressionmodule 58 may compress material 52 to any suitable density within mold54, on some examples, compression module 58 may compress material 52 toa fiber volume density between approximately 17 volume percent materialand approximately 30 volume percent material.

Optionally, material 52 may be needled within mold cavity 55 vianeedling module 62 (254). During a needling operation, one or moreneedles of needling module 62 may retractably extend into at least aportion of mold cavity 55 and material 52 within mold cavity 55 (254).In some examples, the one or more needles may include hooked distal endsthat hook different fibers of material 52 when the one or more needlesare inserted into material 52. Needles 262 may entangle different fibersof material 52 within mold cavity 55. Entangled fibers may resistseparation during subsequent pitch densification. Although the exampleof FIG. 7 includes needling of material 52 after material 52 iscompressed (252), material 52 may be additionally or alternativelyneedled prior to being compressed in mold cavity 55. Further, as notedabove, in some examples, material 52 is not needled in mold cavity 55.

After compressing material 52 within mold cavity 55 (252) and needlingmaterial 52 within mold cavity 55 (254), material 52 may be densifiedwith pitch within mold cavity 55 using a VPI cycle (256). During a VPIcycle, mold cavity 55 of mold 54 may be reduced to vacuum pressure toevacuate the pores of material 52. Mold cavity 55 may then be floodedwith melted pitch. After flooding, a gas such as, e.g., an inertnitrogen gas, may be used to pressurize the pitch within mold cavity 55.In this manner, apparatus 50 may be used to density a material throughone or more cycles of VPI. Overall, in the example of FIG. 7, materialmay be compressed, needled, and densified with pitch all within moldcavity 55 of apparatus.

By processing a material and then pitch densifying the processedmaterial within the same apparatus, the technique of FIG. 7 may allowapparatus 50 to process materials that may not otherwise be fabricatedinto a preform and then pitch densified on a separate apparatus. Forinstance, in some examples, apparatus 50 may be used to process apre-carbonized carbon fiber material or a pitch fiber material that maylack sufficient mechanical strength to be fabricated into a preform. Insome examples, the use of such materials may eliminate carbonizationprocessing such as, e.g., a carbonization step performed duringfabrication of a preform, that may otherwise be performed during thefabrication of a C—C composite component.

Various examples have been described. These and other examples arewithin the scope of the following claims.

1. An apparatus comprising: a mold defining a mold cavity configured toreceive a material to be densified, wherein the mold cavity isconfigured to be adjusted from a first volume to a second volume lessthan the first volume to compress the material in the mold cavity; a gassource configured to apply a gas pressure in the mold cavity to forcepitch into the material in the mold cavity to densify the material; anda vacuum source configured to create a vacuum pressure in the moldcavity at least prior to the application of the gas pressure.
 2. Theapparatus of claim 1, wherein the mold defines a top surface, a bottomsurface, and the mold cavity is defined between the top surface and thebottom surface, and wherein the top surface is configured to actuate toreduce a volume of the mold cavity from the first volume to the secondvolume.
 3. The apparatus of claim 1, further comprising a pressconfigured to adjust a volume of the mold cavity, wherein the press isconfigured to compress the material in the mold cavity to betweenapproximately 15 volume percent material and approximately 50 volumepercent material.
 4. The apparatus of claim 3, wherein the press isconfigured to compress the material in the mold cavity to betweenapproximately 17 volume percent material and approximately 30 volumepercent material.
 5. The apparatus of claim 4, wherein the presscomprises a hydraulic piston configured to actuate a surface of the moldto compress the material in the mold cavity.
 6. The apparatus of claim1, wherein the gas source is configured to apply the gas pressurebetween approximately 10 pounds per square inch (psi) and approximately1000 psi within the mold cavity.
 7. The apparatus of claim 6, whereinthe vacuum source is configured to apply the vacuum pressure betweenapproximately 1 torr and approximately 100 torr within the mold cavity.8. The apparatus of claim 1, wherein the apparatus is configured topitch densify the material to a density between approximately 1.35 gramsper cubic centimeter and approximately 1.5 grams per cubic centimeter.9. The apparatus of claim 1, further comprising a plurality of needlesconfigured to extend into the mold cavity to axially entangle thematerial in the mold cavity.
 10. A method comprising: inserting amaterial a mold cavity of an apparatus, wherein the apparatus isconfigured to densify the material within the mold cavity using a vacuumpressure infiltration cycle; compressing the material in the mold cavityby adjusting the mold cavity from a first volume to a second volume lessthan the first volume; and pitch densifying the compressed material inthe mold cavity using the vacuum pressure infiltration cycle.
 11. Themethod of claim 10, wherein the material to be densified comprises atleast one of a carbonized polyacrylonitrile fiber or a pitch fiber. 12.The method of claim 10, wherein the material comprises a fiber materialformed into a plurality of segments, and wherein inserting the materialinto the mold cavity comprises inserting the plurality of segments todefine a plurality of layers in the mold cavity.
 13. The method of claim10, wherein the mold includes a top surface and a bottom surfacedefining at least a portion of the mold cavity, and wherein insertingthe material into the mold cavity comprises: placing the material ontothe bottom surface of the mold cavity; and placing the top surface ofthe mold over the material on the bottom surface of the mold cavity todefine a bounded volume for pitch densifying the material.
 14. Themethod of claim 13, wherein compressing the material in the mold cavitycomprises actuating the top surface of the mold to compress the materialin the mold cavity.
 15. The method of claim 14, wherein actuating thetop surface of the mold cavity comprises extending a hydraulic pistonconnected to the top surface of the mold.
 16. The method of claim 10,wherein compressing the material comprises compressing the material tobetween approximately 17 volume percent material and approximately 30volume percent material.
 17. The method of claim 10, further comprising,subsequent to inserting the material in the mold cavity, needling thematerial to axially entangle the material in the mold cavity.
 18. Themethod of claim 10, wherein pitch densifying the compressed material inthe mold cavity using the vacuum pressure infiltration cycle comprises:creating a vacuum pressure in the mold cavity between approximately 1torr and approximately 100 torr; filling the mold cavity with meltedpitch; and applying a gas pressure in the mold cavity betweenapproximately 10 pounds per square inch (psi) and approximately 1000pounds per square inch to force the melted pitch into the material. 19.The method of claim 10, wherein pitch densifying the compressed materialcomprises pitch densifying the compressed material to a density betweenapproximately 1.35 grams per cubic centimeter and approximately 1.5grams per cubic centimeter.
 20. The method of claim 10, whereincompressing the material comprises compressing the material to a densitybetween approximately 0.25 grams per cubic centimeter and approximately1 gram per cubic centimeter.